RPT-Chinese deepsea rig returns to work after repairs

BEIJING, March 8 (Reuters) - China's $1-billion deepsea
drilling rig, the first of its kind designed and built at home,
has returned to work in a South China Sea gas field after nearly
two months of repairs, rig owner China National Offshore Oil
Company said on Friday.

The rig, "Offshore Oil 981", was being chartered by Canada's
Husky Energy, operator of the Liwan project in the
western part of South China Sea, a major offshore gas discovery,
industry officials have said.

"Leaks have been repaired and maintenance works finished.
Offshore Oil 981 has returned to works at Liwan 3-1 gas field,"
CNOOC, parent of CNOOC Ltd said in an email.

CNOOC told Reuters last month that "minor leaks" were found
at one water pump room on Dec 31 during routine checks, possibly
caused by the release of structural stress in the early days of
the rig's operation.

CNOOC did not give a final analysis for the leaks. Industry
officials with knowledge of the matter said cracks were found in
one of the rig's four steel columns that had led to water leaks,
which could be due to steel problems or design faults.

The rig, officially launched last May, was dedicated to
exploring the South China Sea, in which China, Vietnam, the
Philippines, Taiwan, Malaysia and Brunei have overlapping
claims.

Before Husky chartered the rig it had drilled several
deepwater wells for CNOOC Ltd, industry officials said.

The rig was built by China's Waigaoqiao shipyard and has a
dual registration, with the China Classification Society (CCS)
and the American Bureau of Shipping (ABS). It is owned by CNOOC
and operated by China Oilfield Services (COSL).